I "closed" the pool last fall using Polyquat per normal methods. The closing consisted of putting on the opaque safety cover and running the pump when too cold to avoid freezing. The cover is a little old and has some tiny holes (less than dime sized) in a few places and doesn't fit perfectly around the ladder (small gaps nothing more than 1/4-1/2 inch in size.
Because of the cover and the polyquat I was hoping to open Algae free... . What I found was a light yellow green dusty mess all over. The Polaris 380 was left in the pool all season and the hoses were slimy and the unit was kinda spotted with algae.
First step - measurements!
CYA: > 0 < 20 (slightly cloudy after several minutes - could still see the dot with the tube all the way full; estimated < 10ppm)
Water: Cloudy and greenish/yellow
Pump PSI: 18
Backwashed; PSI dropped to 14-15
Nothing else measured; last year TA was around 70-80; CH was around 240.
Added 3 bags of AquaChem dichlor shock left over from previous year. Used this to try to get some CYA in since I had none on hand. Did not realize that these were only 58% dichlor; the rest is likely a flocking/clarifier agent as the algae settled to the bottom in short order (by the next day). Originally I thought I was adding about 15ppm of FC and around 13ppm CYA. However now that I realize this was only ~ 28oz of dichlor the add was actually more like: FC +8.6; CYA: +7.8.
3pm Measured again:
Pump PSI: 22!
Backwashed: PSI dropped to 13-14
Water: Cloudy; still greenish; yellow but lighter
Added 2 gallons of UNKNOWN % bleach (father-in-law purchased it!) assumed 5.25% as a guess.
6pm measured again:
Pump PSI: 13-14
Water: still cloudy; not green at all
Added another 2 gallons of the UNKNOWN % bleach - went home.
CLOUDY DAY 4/15
Had Father-in-law add 2 gallons of the Unknown bleach.
CYA: > 0 < 20 (measured on a cloudy day; seemed like it was harder to see the dot when full but still visible)
Pump PSI: 13-14
Water Crystal Clear NOT CLOUDY (yeah! progress) - algae dust on the floor still.
No more bleach added since CYA added was less than originally anticipated. I am treating this as though the CYA was at most 20 for now.
Overcast and Cloudy all morning
Water: As previous; some algae on floor; water clear.
Plan is to toss in more Dichlor (I have several pounds of 99%) as FC falls to 10-11; lack of sun is helping keep the FC high despite the lack of CYA.
Goal is to get CYA up to 30 but slowly so shock is easier to reach and maintain. Treating this like Mustard Algae, once pool is clear clear clear then I will work on trying to remove light and ladder and clean these and toss things like cleaner in for 24 hours at MA shock levels.
Did I miss anything?